Braided Polyester Fiber Core in Steel Wire Rope

ABSTRACT

A wire rope for elevator systems used to hoist, compensate, and govern an elevator car. The wire rope may include six to ten outer steel strands surrounding a central braided polyester core. The wire rope may include six to ten outer steel strands and six to ten inner steel strands surrounding a central braided polyester core. The braided polyester core may include 8-24 single- or double-braided outer strands surrounding a polyester core center that may include parallel fibers, twisted fibers, twisted strands, single-braided strands, or double-braided strands.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 62/348,432, filed Jun. 10, 2016, the disclosure of whichis hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates, in general, to a wire rope and, inparticular, a steel wire rope with a braided polyester fiber core foruse in elevator systems.

Description of Related Art

Wire ropes or elevator ropes are used to hoist, compensate, and governelevator cars within an elevator system and require a high tensilestrength for hoisting and holding the individual elevator cars. Wireropes are typically made by twisting together metallic wires or strandsand typically have a substantially round cross-sectional shape. Currentelevator wire ropes include a rope construction utilizing a textile core(e.g., sisal) with outer steel strands wound thereon. These wire ropesare designed to have a predetermined weight per unit length for eachrope size. The elevator operation and functioning, such as requiredmotor power, friction characteristics, and payload that can be lifted,are based on such specific weight that usually can vary by ±5%, but notmore unless the design of the elevator operation is modified.

The geometry or configuration of a wire rope cross-section and methodand material of its manufacture are precisely designed to perform in apredetermined manner and to a predetermined end. The core of the wirerope is the foundation of the wire rope and the core material may benatural or synthetic. Consistency of the diameter and even wear of thewire rope is important in an elevator system due to the wire ropes beingused in a parallel configuration of between 2-14 wire ropes. If all ofthe rope diameters are not consistent and the wear of the individualwire ropes is uneven, the safety of the passengers in the elevator carsmay be compromised. Ropes with diameters that vary can vibrate and causenoise, which creates an unpleasant ride for passengers in the elevatorcar and the elevator cars may bounce more at the start-up and stoppingpoints in the elevator system. The inconsistent and uneven wire ropescan damage sheaves or pulleys in the elevator system costing thecustomer additional costs in repair or replacement.

Consistency of the diameter of the wire rope throughout allenvironmental conditions is an important feature. Wire rope diametersshould always remain consistent to ensure a safe and smooth ride and tosave wear and tear on other, more expensive parts of the elevatorsystem. The ability to maintain a diameter in humid and/or wetconditions is a benefit to wire ropes that helps to lengthen the servicelife of the wire rope. Wire ropes with twisted sisal cores absorb largeamounts of water and condensation and often increase in diameter due toswelling in humid and/or wet conditions. Water softens the natural sisalfiber and reduces the support provided by the core to the outer steelstrands, which causes a short service life for the wire rope. Typically,even upon drying, a wire rope with a twisted sisal core will remainslightly swelled from its original diameter.

Currently, all sisal core wire ropes are lubricated with a light oil.Depending on the origin of the oil, the oil can be 7-13% of the coreweight. It is often difficult to obtain a consistent lubrication contentthroughout a continuous length of twisted sisal material. Inconsistentand high lubrication contents from a sisal rope manufacturer can causeproblems during the manufacturing of wire ropes and for end users of thewire ropes. High lubrication content can be squeezed out of the core ofthe wire rope during a closing process of the wire rope or during theuse of the wire rope in an elevator system. In the event the lubricationsqueezes out while in the elevator system, the lubrication can mix withthe lubrication put on the outer steel strands of the wire rope and candisplace from the wire rope. This typically creates a mess in themachine room, elevator shafts, basements, and elevator cars. Manyelevator systems are provided in high priced, high profile buildings,and building owners do not want their buildings messy with grease fromwire ropes.

Sisal is a naturally grown fiber making the fiber diameters anddensities uncontrollable and often inconsistent. When these fibers ofdifferent diameters and densities are twisted together to make a sisalcore, a rather inconsistent wire rope is formed. Subsequently,lubrication is added to the sisal core, which also adds weight and cancause lubrication issues as discussed above. Therefore, using a sisalcore can often create an inconsistent wire rope along its length, withdifferent diameters and densities. It is often difficult to provide aconsistently round and safe wire rope throughout the length of aproduction run and between production runs.

Therefore, a problem to be solved is the need to provide the elevatorindustry with a more consistent product. A more consistent product canlessen or eliminate issues such as vibration, premature rope wear,lubrication issues, and diameter reduction in the wire rope. Lesseningor eliminating these issues, in turn, provides a better, longer servicelife for both the wire rope and any peripheral equipment. These issuesare currently addressed by closely monitoring the wire ropes to checkfor premature rope wear and diameter reduction, checking tensions forequalization to reduce vibration, and lubricating, or wiping ropes iflubrication is needed or in excess while wire ropes are operating in theelevator systems.

SUMMARY OF THE INVENTION

In view of the foregoing, a need exists for a wire rope with a rounder,more consistent core that will produce a rounder, more consistent wirerope. A further need exists for a wire rope that includes a core thatprevents or reduces moisture absorption in the wire rope. An evenfurther need exists for a wire rope that removes the need forlubrication in the core of the wire rope. Lastly, there is a need for awire rope that includes a core that provides a consistent diameter anddensity along its length.

In one aspect of the disclosure, an elevator wire rope may include abraided polyester core and at least six outer strands provided aroundthe braided polyester core.

In another aspect, the polyester core may have a plurality ofsingle-braided outer strands. The polyester core may have a plurality ofdouble-braided outer strands. Underlying layers of the braided polyestercore may have a parallel configuration, a twisted configuration, asingle-braided configuration, or a double-braided configuration. Six toten outer strands may be provided around the braided polyester core. Theouter strands may be made of steel. The outer strands may include acentral wire, at least four intermediate wires surrounding the centralwire, and at least four exterior wires surrounding the intermediatewires. The braided polyester core may include an inner core with aplurality of braided strands and an outer core with a plurality ofbraided strands. The braided strands of the inner core may be eithersingle-braided or double-braided. The braided strands of the outer coremay be either single-braided or double-braided. The braided polyestercore may include an inner core with a plurality of twisted strands andan outer core with a plurality of braided strands. The braided strandsof the outer core may be either single-braided or double-braided. Thebraided polyester core may include an inner core with a plurality ofstrands extending parallel to a longitudinal length of the elevator wirerope and an outer core with a plurality of braided strands. The braidedstrands of the outer core are either single-braided or double-braided.

In another aspect, an elevator wire rope may include a braided polyestercore comprising an inner core and an outer core, and at least six outerstrands provided around the braided polyester core, each outer strandmay include a central wire, at least four intermediate wires surroundingthe central wire, and at least four exterior wires surrounding theintermediate wires.

In another aspect, the braided polyester core may include an inner corewith a plurality of braided strands and an outer core with a pluralityof braided strands. The braided strands of the inner core may be eithersingle-braided or double-braided. The braided strands of the outer coremay be either single-braided or double-braided. The braided polyestercore may include an inner core with a plurality of twisted strands andan outer core with a plurality of braided strands. The braided strandsof the outer core may be either single-braided or double-braided. Thebraided polyester core may include an inner core with a plurality ofstrands extending parallel to a longitudinal length of the elevator wirerope and an outer core with a plurality of braided strands. The braidedstrands of the outer core are either single-braided or double-braided.

These and other features and characteristics of the wire rope willbecome more apparent upon consideration of the following description andthe appended claims with reference to the accompanying drawings, all ofwhich form a part of this specification, wherein like reference numeralsdesignate corresponding parts in the various drawings. It is to beexpressly understood, however, that the drawings are for the purposes ofillustration and description only and are not intended as a definitionof the limits of the invention. As used in the specification and theclaims, the singular form of “a”, “an”, and “the” include pluralreferents unless the context clearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a wire rope according to the presentinvention;

FIG. 2 is a side view of a braided polyester core of the wire rope ofFIG. 1 next to a twisted sisal fiber core according to the prior art;

FIG. 3A shows a side view of a single- or double-braided polyester coreconstruction;

FIG. 3B shows a side view of a twisted polyester core construction;

FIG. 3C shows a side view of a parallel polyester core construction;

FIG. 4 is a chart illustrating results of a water soak test performed ona polyester rope according to the present disclosure and a sisal rope;

FIG. 5A is a chart illustrating comparisons of tested sisal ropediameters and densities to manufacturer's certification requirements fora sisal rope diameter and density; and

FIG. 5B is a chart illustrating comparisons of tested polyester ropediameters and densities to manufacturer's certification requirements fora polyester rope diameter and density.

DESCRIPTION OF THE DISCLOSURE

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal”, and derivatives thereof shall relate to the invention asit is oriented in the drawings. However, it is to be understood that theinvention may assume alternative variations and step sequences, exceptwhere expressly specified to the contrary. It is also to be understoodthat the specific aspects and processes illustrated in the attacheddrawings, and described in the following specification, are simplyexemplary aspects of the invention. Hence, specific dimensions and otherphysical characteristics related to the invention disclosed herein arenot to be considered as limiting.

The present disclosure is directed to, in general, a wire rope used tohoist elevator cars in an elevator system and, in particular, to a wirerope having a braided polyester core.

With reference to FIG. 1, a wire rope 2 according to the presentdisclosure is described. The wire rope 2 may include a plurality ofouter strands 4 that surround a core 6. In one embodiment, eight (8)outer strands 4 may surround the core 6. It is contemplated, however,that alternative numbers of outer strands 4 may surround the core 6. Forexample, the number of outer strands 4 provided around the core 6 mayrange from 6-10 outer strands 4. The wire rope 2 may have asubstantially circular cross-sectional shape. In one aspect, the outerstrands 4 may be made of steel. It is contemplated, however, thatalternative materials may be used for the outer strands 4. Each outerstrand 4 may include a central wire 8 surrounded by a plurality ofintermediate wires 10. The plurality of intermediate wires 10 may besurrounded by a plurality of exterior wires 12. In one aspect, the outerstrands 4 may have a specific color to correspond to a certain type ofwire rope 2 for identification purposes by a vendor or manufacturer.

With reference to FIG. 2, the core 6 may be made of polyester. It isalso contemplated that alternative materials, such as polypropylene, maybe used to form the core 6. In one aspect, the core 6 may be braided.The core 6 may be made of single-braided or double-braided strands. Inone aspect, a single-braided strand includes a plurality of strandsbraided within one another. In one aspect, a double-braided strandincludes a central member and a plurality of strands braided around thecentral member. In one aspect of the disclosure, a wire rope 2 forhoisting an elevator car may include a braided polyester core 6 andbetween 6 and 10 outer steel strands 4. There may be an intermediatelayer of between 6 and 10 steel strands between the braided polyestercore 6 and the outer steel strands 4. The braided polyester core 6 mayhave a minimum of 8 and a maximum of 24 single- or double-braided outerstrands. The braided core 6 polyester construction beneath the braidedouter strands may be parallel, twisted, single-braided, ordouble-braided or a combination of parallel, twisted, single-braided, ordouble-braided. These types of construction are illustrated in FIGS.3A-3C.

As shown in FIGS. 3A-3C, the core 6 of the wire rope 2 may include aninner core 18 and an outer core 16. Both of the inner core 18 and theouter core 16 may be made of polyester strands. In one aspect shown inFIG. 3A, the core 6 may be a braided polyester core. The core 6 mayinclude a single- or double-braided inner core 18 and a single- ordouble-braided outer core 16. The inner core 18 and/or the outer core 16may include a plurality of single-braid strands or double-braid strands.In another aspect shown in FIG. 3B, the core 6 may have a twisted innercore 18 and a single- or double-braided outer core 16. The outer core 16may be made of single-braid strands or double-braid strands. The twistedinner core 18 may twist or wrap around a central axis runninglongitudinally through the core 6. In another aspect shown in FIG. 3C,the core 6 may have an inner core 18 with a parallel configuration thatdoes not include a braid and an outer core 16 that includes a single- ordouble-braid. The outer core 16 may be made of single-braid strands ordouble-braid strands. The parallel configuration of the inner core 18may include polyester fibers that run parallel to a longitudinal lengthof the wire rope 2. By utilizing a polyester core in the wire rope 2, arounder, more consistent core is provided for the wire rope 2, which inturn provides a rounder, more consistent wire rope 2. A rounder and moreconsistent wire rope 2 will wear more evenly in the elevator system.Consistency of diameter and even wear of the wire rope 2 is important inan elevator system due to the wire ropes 2 being used in a parallelconfiguration of between 2-14 ropes. By using a braided polyester core 6including 8-24 outer strands 4 with specified diameters and densities asopposed to a core of 3 or 4 strands of twisted sisal, polyester, orpolypropylene, the steel outer strands 4 can rest on a rounder core 6and the outer strand-to-core pressures can be equalized allowing for arounder wire rope 2 that will wear more evenly. The benefits of a moreconsistent diameter and even wire rope wear are an enhanced ridequality, enhanced ride safety, the wire rope 2 is easier to produce,customers can save money on installation costs of the wire rope 2,customers can save money by not damaging other parts of the elevatorsystem, and customers can save money by increasing the service life ofthe wire rope 2. A wire rope utilizing a sisal fiber core does notprovide these advantages that are provided by a wire rope 2 with abraided polyester core 6. The braided polyester core 6 may have specificdimensions and density to ensure that the wire rope 2 is sufficient forhoisting, compensating, and governing an elevator car. Each size ofpolyester rope maintains a consistent diameter and density along itslength. Unlike the polyester rope, the sisal fiber rope used in currentwire ropes typically has an inconsistent diameter and density along itslength that produces an inconsistent diameter and density for the entirewire rope. Further, the braided polyester core 6 requires no oil orlubrication, thereby eliminating any lubrication problems that aretypically experienced when using a twisted sisal fiber core 14.

With reference to the chart in FIG. 4, a wire rope 2 including a braidedpolyester core 6 maintains a more consistent diameter duringwater/humidity absorption than a wire rope including a sisal fiber core14 (shown in FIG. 2). Testing on water absorption into a braidedpolyester core 6 and a twisted sisal fiber core 14 was conducted tocompare each core's ability to maintain diameter during the waterabsorption. Samples of each core were weighed and the diameter of eachsample was measured. For example, an average pre-soak diameter for thelength of single-braid polyester core 6 was 0.3095 inches and an averagepre-soak diameter for the length of double-braid polyester core 6 was0.3185 inches. The average pre-soak diameter for the length of twistedsisal fiber core 14 was 0.337 inches. The samples were then submerged inwater for 24 hours and re-weighed and measured for diameter. The braidedpolyester core 6 gained approximately 20% of its weight in water, butthe water was not absorbed in the braided polyester core 6. The waterwas caught in between very small synthetic fibers in the core 6. Thediameter of the braided polyester core 6 did not increase. The averagepost-soak diameter for the length of single-braid polyester core 6 was0.3100 inches and the average post-soak diameter for the length ofdouble-braid polyester core 6 was 0.3195 inches. The water trappedin-between the fibers of the braided polyester core 6 had no ill effectson the strength or integrity of the braided polyester core 6. Thetwisted sisal fiber core 14 absorbed approximately 61% of its weight inwater and swelled 23% in diameter. The average post-soak diameter forthe length of twisted sisal fiber core 14 was 0.414 inches. The watersoftened the natural sisal fibers and caused the twisted sisal fibercore 14 to provide less support for the outer steel strands and createda shorter service life for the wire rope.

Both of the samples were then allowed to air dry for 24 hours. Thebraided polyester core 6 dried completely with no change in diameter.The average dried diameter for the length of single-braid polyester core6 was 0.3100 inches and the average dried diameter for the length ofdouble-braid polyester core 6 was 0.3195 inches. The twisted sisal fibercore 14 almost dried completely, but the diameter remained swelled to+20% of the original diameter. The average dried diameter of the lengthof twisted sisal fiber core 14 was 0.403 inches. Therefore, the braidedpolyester core 6 provides a more consistent wire rope 2 throughout allenvironmental conditions to ensure a safe and smooth ride and to reducewear on other, more expensive parts of the elevator system. The abilityto maintain a diameter in humid and/or wet conditions is an advantagethat a wire rope 2 with a braided polyester core 6 can provide toincrease the service life of the wire rope 2. A wire rope with a twistedsisal fiber core 14 will have an inconsistent diameter along its lengthin humid/wet conditions due to the swelling of the twisted sisal fibercore 14. The inconsistent diameter will increase the wear on the wirerope and shorten the service life of the wire rope. A wire rope 2 with abraided polyester core 6 improves over this type of wire rope to providea more consistent wire rope diameter.

The chart shown in FIG. 5A illustrates certificate diameters anddensities for sisal fiber ropes that are typically requested fromvendors. Manufacturers of wire rope typically request sisal fiber ropeshaving these certified diameters and densities to use in wire rope forelevator systems. As illustrated in the chart of FIG. 5A, thecertificate diameters and densities typically fall within predeterminedspecification tolerances. However, upon delivery to the manufacturers,the sisal fiber rope does not typically have the requested certificatediameters and densities. A number of samples of sisal fiber rope ofvarying sizes were measured upon receipt from a vendor. As shown in thechart of FIG. 5A, the tested diameters and densities of the samples uponreceipt from the vendor did not correspond to the requested certificatediameters and densities. On average, the difference between the testeddiameters and the certificate diameters was +2.59%. On average, thedifference between the tested densities and the certificate densitieswas +5.03%. The positive percentages show that the tested diameters anddensities are below the values stated on the vendor's certificates.Although the tested diameters were still within the specificationtolerances, the tested diameters were not close to the requestedcertificate diameters. It was also determined that the tested densitiesdid not pass incoming inspection and did not fall within thespecification tolerances. Therefore, the chart of FIG. 5A illustratesthe inconsistency in the diameter and density of sisal fiber rope thatis provided from vendors. Sisal is a naturally grown fiber making thefiber diameters and densities uncontrollable. When the fibers ofdifferent diameters and densities are twisted together to make a twistedsisal fiber core 14, the core 14 makes an inconsistent rope. Further,lubrication is added to the sisal rope, which also adds weight to therope.

The chart shown in FIG. 5B illustrates certificate diameters anddensities for polyester ropes that are typically requested from vendors.As illustrated in the chart of FIG. 5B, the certificate diameters anddensities typically fall within predetermined specification tolerances.Unlike the sisal fiber rope, upon delivery to the manufacturers, thepolyester rope has the requested certificate diameters and densities. Anumber of samples of polyester rope of varying sizes were measured uponreceipt from a vendor. As shown in the chart of FIG. 5B, the testeddiameters and densities of the samples upon receipt from the vendorcorresponded to the requested certificate diameters and densities. Onaverage, the difference between the tested diameters and the certificatediameters was −1.17%. On average, the difference between the testeddensities and the certificate densities was −1.02%. The negativepercentages show that the tested diameters and densities are above thatwhich was stated on the vendor's certifications. All of the polyesterrope samples passed incoming inspection and the tested diameters anddensities were very consistent and close to the vendor certificatediameters and densities. Synthetic fibers, such as the polyester core 6,are extruded to the same density and diameter every time, which makesthe process and outcome highly repeatable and consistent. Therefore, thespecifications for the wire rope 2 can remain consistent, which isimportant in order to produce a consistently round and safe wire rope 2throughout the length of a production run and between production runs.

While various aspects of the wire rope 2 were provided in the foregoingdescription, those skilled in the art may make modifications andalterations to these aspects without departing from the scope and spiritof the invention. For example, it is to be understood that thisdisclosure contemplates that, to the extent possible, one or morefeatures of any aspect can be combined with one or more features of anyother aspect. Accordingly, the foregoing description is intended to beillustrative rather than restrictive. The invention describedhereinabove is defined by the appended claims and all changes to theinvention that fall within the meaning and the range of equivalency ofthe claims are to be embraced within their scope.

The invention claimed is:
 1. An elevator wire rope comprising: a braidedpolyester core; and at least six outer strands provided around thebraided polyester core.
 2. The elevator wire rope as claimed in claim 1,wherein the polyester core has a plurality of single-braided outerstrands.
 3. The elevator wire rope as claimed in claim 1, wherein thepolyester core has a plurality of double-braided outer strands.
 4. Theelevator wire rope as claimed in claim 1, wherein underlying strands ofthe braided polyester core have a parallel configuration, twistedconfiguration, a single-braided configuration, or a double-braidedconfiguration.
 5. The elevator wire rope as claimed in claim 1, whereinsix to ten outer strands are provided around the braided polyester core.6. The elevator wire rope as claimed in claim 1, wherein the outerstrands are made of steel.
 7. The elevator wire rope as claimed in claim1, wherein the outer strands comprise: a central wire; at least fourintermediate wires surrounding the central wire; and at least fourexterior wires surrounding the intermediate wires.
 8. The elevator wirerope as claimed in claim 1, wherein the braided polyester corecomprises: an inner core with a plurality of braided strands; and anouter core with a plurality of braided strands.
 9. The elevator wirerope as claimed in claim 8, wherein the braided strands of the innercore are either single-braided or double-braided, and wherein thebraided strands of the outer core are either single-braided ordouble-braided.
 10. The elevator wire rope as claimed in claim 1,wherein the braided polyester core comprises: an inner core with aplurality of twisted strands; and an outer core with a plurality ofbraided strands.
 11. The elevator wire rope as claimed in claim 10,wherein the braided strands of the outer core are either single-braidedor double-braided.
 12. The elevator wire rope as claimed in claim 1,wherein the braided polyester core comprises: an inner core with aplurality of strands extending parallel to a longitudinal length of theelevator wire rope; and an outer core with a plurality of braidedstrands.
 13. The elevator wire rope as claimed in claim 12, wherein thebraided strands of the outer core are either single-braided ordouble-braided.
 14. An elevator wire rope comprising: a braidedpolyester core comprising an inner core and an outer core; and at leastsix outer strands provided around the braided polyester core, each outerstrand comprising: a central wire; at least four intermediate wiressurrounding the central wire; and at least four exterior wiressurrounding the intermediate wires.
 15. The elevator wire rope asclaimed in claim 14, wherein the inner core comprises a plurality ofbraided strands; and wherein the outer core comprises a plurality ofbraided strands.
 16. The elevator wire rope as claimed in claim 15,wherein the braided strands of the inner core are either single-braidedor double-braided, and wherein the braided strands of the outer core areeither single-braided or double-braided.
 17. The elevator wire rope asclaimed in claim 14, wherein the inner core comprises a plurality oftwisted strands; and wherein the outer core comprises a plurality ofbraided strands.
 18. The elevator wire rope as claimed in claim 17,wherein the braided strands of the outer core are either single-braidedor double-braided.
 19. The elevator wire rope as claimed in claim 14,wherein the inner core comprises a plurality of strands extendingparallel to a longitudinal length of the elevator wire rope; and whereinthe outer core comprises a plurality of braided strands.
 20. Theelevator wire rope as claimed in claim 19, wherein the braided strandsof the outer core are either single-braided or double-braided.